Now ratings body the British Board of Film Classification (BBFC) has received its first ever complaint about the U-rated movie.

But the moment which got the viewer steamed up was not when Jenny Agutter gasps "Daddy, my Daddy", prompting uncontrolled blubbing, instead it was the fear that it could encourage youngsters to play on railway lines.

However the BBFC, which has classified movies for a century, points out that the film illustrates the dangers all too clearly and is set in a very different time.

The 1970 film, which stars Agutter, Bernard Cribbins and Dinah Sheridan, has been a festive favourite for many years and is widely regarded as one of British cinema's treasures.

Based on the E Nesbit novel, it was filmed on the Keighley and Worth Valley Railway - masquerading as the Great Northern and Southern Railway - and chronicles the adventures of three children when they are forced to move from London to Yorkshire after their father is imprisoned for being falsely accused of selling state secrets.

The scene in which Bobbie (played by Agutter) rushes to embrace her released father on the platform at Oakworth station is imprinted on the minds of anyone who has seen it. But in some scenes the children are seen on the tracks, notably as they attempt to warn a train driver about a landslide, and rescuing a young boy who has hurt his leg in a tunnel during a paperchase, with near-disastrous consequences.

The complaint about the footage is revealed in the BBFC's annual report, which notes: "The correspondent was concerned that children may be encouraged to play on railway tracks as a result of seeing the film. While aware of the real dangers of such behaviour, the BBFC judged that it was very unlikely that The Railway Children would promote such dangerous activity.

"The Railway Children is set in the Edwardian period and trains and access to railway property are very different today. The film also demonstrates the potential harm to children if proper care is not taken."

The most complained-about film of the year was The Woman In Black, which prompted 134 people to grumble the film was "too dark and unsettling" for its 12A certificate. The report notes that one of the factors had been that it starred Daniel Radcliffe, best known for his Harry Potter role, who would have attracted younger cinemagoers who may not have been prepared for the content.